1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each comprising the electrophotographic photosensitive member. Particularly, the present invention relates to an electrophotographic photosensitive member comprising a surface layer containing a specified silicone resin, and a process cartridge and an electrophotographic apparatus each comprising the electrophotographic photosensitive member.
2. Description of the Related Art
An electrophotographic photosensitive member is required to have sensitivity, electric characteristics and optical characteristics according to the electrophotographic process used. Particularly, the repeated use of an electrophotographic photosensitive member causes direct application of electric and mechanical external forces for charging, image exposure, toner development, transfer, cleaning, etc., and thus durability against these forces is also required. Specifically, durability is required against chemical deterioration due to ozone and nitrogen compounds produced in charging, and mechanical and electric deterioration due to discharge during charging and sliding friction of a cleaning member.
Unlike an inorganic photosensitive member, an electrophotographic photosensitive member comprising a relatively soft material containing an organic photoconductive substance exhibits low durability against mechanical deterioration, and thus various attempts have been made to satisfy durability characteristics.
Particularly, as a method for effectively preventing mechanical deterioration to improve durability, the friction coefficient of the surface of an electrophotographic photosensitive member is decreased by containing a fluororesin powder in the surface layer of the electrophotographic photosensitive member. This method causes smooth sliding friction with a cleaning member, thereby preventing application of strong shear stress to the surface of the electrophotographic photosensitive member.
However, a fluororesin powder has low surface tension, and is thus difficult to uniformly disperse in a resin having relatively high surface tension. Therefore, combinations with various auxiliary dispersants are proposed. However, while many of commercially available auxiliary dispersants have excellent dispersibility for fluororesins, and thus have complicated structures, they cause difficulties in stabilizing secondary aggregations of a fluororesin during dispersion. This problem is particularly significant in an electrophotographic photosensitive member having a thin surface layer having a thickness of about 1 to 100 .mu.m, causing spots or fogging in an image.
The auxiliary dispersant also causes a potential change due to carrier trapping.